The present invention relates to a digital recording/reproduction apparatus for recording/reproducing digital image data which is high-efficiency coded, to/from a random access recording medium such as an A/V-HDD (Audio/Video-Hard Disk Drive).
As for digital recording/reproduction apparatus, as a high-efficiency coding method for compressing image data, MPEG2 (Moving Picture Experts Group 2) system attracts attention as technology for realizing digital broadcasting. A stream of images/voices coded according to MPEG2 system comprises elementary streams. In addition, the elementary streams having a common time base are called a program. The elementary stream is divided and incorporated in a data structure of a PES (Packetized Elementary Stream) packet, and the PES packet is further combined with a PES packet having the common time base, to be a program stream. A single bit sequence which is obtained by combining program streams having one or more time bases is called a transport stream and utilized in the digital CS broadcasting and the like.
Since image data coded according to MPEG2 is created on the basis of previous and subsequent image data, information is not complete in only one image. Therefore, the random access is performed with a GOP (Group of Picture) comprising image data of several frames as a unit.
FIG. 6 is a diagram showing arrangement of respective types of images in a GOP according to MPEG2 system. FIG. 7 is a diagram showing an image displaying order by a decoding process according to MPEG2 system.
As shown in FIG. 6, the GOP includes at least one I picture (intra-picture coded image). The I picture is obtained by coding image data corresponding to a picture by DCT (Discrete Cosine Transform) and quantization. The I picture is an image which is coded only by its information and it is generated without using inter-picture prediction. An image every predetermined cycle M starting from this I picture is converted into a P picture (inter-picture prediction coded image) by forward inter-picture prediction coding. These I and P pictures are coded in the same order as that of original images. In addition, each of image data between the I picture and P picture or the P pictures is converted into a B picture (bidirectional prediction coded image) by bidirectional prediction coding using the forward and backward image data (I picture and P picture). The B picture is coded after the I and P pictures are coded.
A PES packet having digital data which is coded according to MPEG2 system is recorded on a recording medium, in the above-described construction.
When the image data is to be decoded, as shown in FIG. 7, the I picture which is coded only by the data within the picture is initially decoded, then the P pictures which are coded using the forward inter-picture prediction are decoded, and finally the B pictures which are coded using the bidirectional prediction are decoded. Reproduction images are reproduced in order of B0, B1, I1, B2, B3, P0, B4, B5, P1, . . . in the direction of time t.
In MPEG2 coding system, since coded data of each I, P, and B picture has a variable length, the position of the I picture which can be decoded only by the data within that picture cannot be specified. A digital recording/reproduction apparatus having data which is coded according to MEPG2 system, recorded on a recording medium such as an A/V-HDD reproduces successively the I, P, and B pictures at the normal playback, whereby image data is reliably reproduced. However, in this digital recording/reproduction apparatus, since the respective I, P, and B pictures are not successively reproduced at the trick playback such as the reverse playback or the time search, the I picture is not always reproduced reliably. When the I picture cannot be reproduced reliably, the P and B pictures using the prediction coding cannot be reproduced either. That is, input image data which is intra-picture/inter-picture coded like MPEG, does not have a uniform data amount for each picture, and with respect to the image data which is inter-picture coded, decoding of image signals cannot be performed directly. Therefore, when the data which is inter-picture coded is recorded on the recording medium and the trick playback such as the reverse playback or time search is performed, only a part of the data on the recording medium is reproduced or reading from the recording medium is late for the reproduction, whereby image data cannot be reproduced reliably.
Japanese Published Patent Application No.Hei.9-247623 discloses a xe2x80x9crecording/reproduction apparatusxe2x80x9d comprising: recorded data reconstruction means for selecting, from video coded data which is obtained by multiplexing intra-frame coded data and inter-frame coded data, the intra-frame coded data and its accompanying header information and program information describing contents of the coded data, to reconstruct the intra-frame coded data and its accompanying header information and the program information; recording means for recording an output from the recorded data reconstruction means in a predetermined position on a recording medium; reproduction means for reproducing the data recorded on the recording medium by the recording means at a predetermined double-speed, to output reproduced data; and reproduced data reconstruction means for selecting the intra-frame coded data and its accompanying header information and the program information, which is reconstructed and recorded, from the output of the reproduction means, to store and reconstruct the same. This recording/reproduction apparatus detects intra-picture coded image data, creates new image data for each trick playback speed, and records plural pieces of image data for trick playback, separately from data for the normal playback. Therefore, this xe2x80x9crecording/reproduction apparatusxe2x80x9d has a complicated circuit configuration for creating new intra-picture coded image data for each trick playback speed, and further records plural pieces of trick playback image data separately from the normal playback data. Therefore, the amount of data recorded on the recording medium is enormous.
It is an object of the present invention to provide a digital recording/reproduction apparatus which can reliably obtain intra-picture coded data and perform trick playback smoothly, without complicating a circuit configuration or significantly increasing a data amount on the recording medium.
Other objects and advantages of the present invention will become apparent from the detailed description and specific embodiments described are provided only for illustration since various additions and modifications within the spirit and scope of the invention will be apparent to those of skill in the art from the detailed description.
According to the present invention, a digital recording/reproduction apparatus for recording/reproducing digital image data, by storing a PES packet in which intra-picture coded data and inter-picture coded data which are compressed digital image data are multiplexed and packetized, on a recording medium by PES packet storing means, as well as reading the PES packet stored on the recording medium by PES packet reading means, comprises: PES header detection means for detecting a video PES header from the PES packet recorded on the recording medium; I picture detecting means for detecting intra-picture coded data from a data part of the PES packet recorded on the recording medium; a counter for determining the number of digital image data in the data part of the PES packet recorded on the recording medium; index file creation means for creating an index file containing header information of the PES packet obtained from the output of the PES header detection means, information indicating the intra-picture coded data obtained from the output of the I picture detection means, and information of the number of the digital image data obtained from the output of the counter; index file storage means for recording the index file created by the index file creation means, on the recording medium; user interface control means for receiving a playback command as an input; index file reading means for reading the index file recorded on the recording medium; and navigation control means for, when a trick playback command is input to the user interface control means, instructing the index file reading means to read the index file on the recording medium to obtain the index file via the index file reading means, referring to the header information of the PES packet to be trick-played, the information indicating the intra-picture coded-data, and the information of the number of the digital image data, in the index file, and controlling reproduction of the digital image data recorded on the recording medium, in accordance with types of the trick playback command input to the user interface control means. Thereby, in the trick playback process, the intra-picture coded data can be obtained reliably from the PES packet which is trick-played. Therefore, the inter-picture coded data using the prediction coding can also be reproduced reliably, whereby the trick playback can be performed smoothly without the loss or delay of image data.
Further, on a recording side of the apparatus, the index file for indicating the intra-picture coded data in the PES packet is created by the index file creation means, to perform the trick playback smoothly. This index file is created on the basis of the information obtained from the outputs of the PES header detection means, the I picture detection means, and the counter. Therefore, this can be realized by a simpler configuration than that of an apparatus which creates plural pieces of image data for trick playback separately from image data for normal playback, such as the xe2x80x9crecording/reproduction apparatusxe2x80x9d disclosed in Japanese Published Patent Application No.Hei.9-247623. Besides, the index file is only-index information of the video PES header or the intra-picture coded data position in the PES packet or the like. Therefore, the data capacity occupied by the index file on the recording medium is reduced.
Furthermore, on a reproduction side of the apparatus, in the trick playback process such as the reverse playback or time search, the intra-picture coded data position in the PES packet is obtained from the index file by the navigation control means. Thereby, the intra-picture coded data can be obtained reliably from the PES packet which is trick-played. Therefore, the inter-picture coded data using the prediction coding can also be reproduced reliably, whereby the trick playback can be performed smoothly without the loss or delay of the image data.